The present invention is generally directed to a cardioverting system and method for providing temporary cardioversion of the heart of a heart surgery patient following a heart surgery procedure. The present invention is more particularly directed to such a system and method for providing post-surgery cardioversion of the atria of the heart.
There are approximately four hundred thousand (400,000) heart surgery procedures performed annually in the United States. The types of such surgical procedures vary from coronary artery bypass grafts to valve replacements, to repair of congenital heart defects. In order to gain access to the heart, these surgeries require the chest to be opened in the middle of the sternum. An incision is then made in the pericardial sac (pericardium) to expose the heart and permit the required surgical procedure to be performed. Following the surgical procedure, the pericardial incision is reapproximated (closed except for a drain opening) with sutures and the chest cavity is closed.
Often, following such heart surgical procedures, the patients' hearts during recovery experience bradycardia or slow heart rates. In the prior art, to overcome such maladies, the hearts of post-surgical heart patients are temporarily paced for a few days following surgery, when required, to maintain the heart rates at a normal rate. This is accomplished by releasably attaching heart wires to the heart before the pericardium is sutured and the chest cavity is closed. First and second heart wires are attached to the myocardium of one of the ventricles such as the left ventricle. The heart wires are then brought outside of the chest. Thereafter, the pericardium is sutured and the chest cavity is closed. The proximal ends of the heart wires are then coupled to a temporary pacemaker to permit the heart to be paced. After the patient has recovered sufficiently wherein pacing is no longer required, the heart wires are pulled out of the patient.
Unfortunately, twenty to thirty percent of all heart surgical patients experience an arrhythmia called atrial fibrillation during the immediate or early post-surgical period. When this occurs, the heart beats rapidly and irregularly. According to reports, this constitutes a major clinical problem resulting in hypotension, heart failure, pneumonia and/or stroke, due to thromboembolism. Hence, such a condition is of great concern to the physician and it is therefore in the best interest of the patient to terminate this arrhythmia as soon as possible.
The development of post-surgical atrial fibrillation has not been associated with preoperative or postoperative events. Further, the specificity and sensitivity of age and other possible relevant factors for prediction of atrial fibrillation after heart surgery is low. No effective prophylactic regimen has yet been established.
When atrial fibrillation of a surgical patient's heart occurs during surgery, the physician terminates the fibrillation by cardioverting the heart. In this cardioversion procedure, the physician contacts each atria with a spoon-sized conductive paddle which is coupled to an external defibrillator. The external defibrillator includes a storage capacitor which is charged to a selected voltage. When the storage capacitor is fully charged, the stored energy is discharged into the atria of the heart through the paddles.
While the above-mentioned cardioverting process is very effective in terminating atrial fibrillation occurring during surgery, this procedure is not available to the physician for terminating atrial fibrillation occurring after the heart surgery is completed and the patient's chest cavity has been closed. It has been observed that the peak incidence of atrial fibrillation is during the second or third postoperative day. While external cardioversion is an option, because the patient's chest cavity at this time is closed, much larger paddles and much greater cardioverting energies must be used as compared to the paddle size and cardioverting energies employed during surgery. Such energies, generally between 50 and 360 joules, would also require that the patient be briefly anesthetized or very heavily sedated prior to attempted external cardioversion. Hence, while external cardioversion, using much larger paddles and much higher cardioverting energies, is available to the physician as an option, most physicians are reluctant to use such external cardioversion because of the likely trauma and tissue damage it would cause the patient during a time in which the patient is in initial recovery from serious open heart surgery.
Drug therapy is also an available option. Its use however is often attended with significant side effects. In addition, there is a substantial potential interaction of such drugs with the many different types and amounts of other drugs the patient is already being given during this initial recovery period.
Hence, there remains a long felt need in the art for a cardioverting system and method capable of arresting fibrillation, such as atrial fibrillation, occurring during the post-heart surgery period. More specifically, there is a need in the art for such a system and method which does not cause prolongation of the patient's recovery period due to trauma and tissue damage and which avoids the need for drug therapy to treat such a condition.